Electrooptical system



R. V. L. HARTLEY ELECTROOPTICAL SYSTEM Dec. 30, 1930.

' 2 Sheets-Sheet 1 Filed Oct. 16, 1928 E w v M Q w Q Am @A A w. x mm msm g mg m Q 3 h A AME M A k w B M ma /N|/N7"UR RL L. HARTLEY BY MwL Dec.3@, i930; Riv. HARTLEY 1,786,652

ELEGTROOPTICAL SYSTEM Filed Oct. 16, 1928 2 Sheets-Sheet 2 Fla. 5

R ML. HARTLEY BY WTURNE V Patented Dec. 30, 1930 UNITED STATES PATENTOFFICE RALPH V. L. HARTLEY OF SOUTH ORANGE, NEW JERSEY, ASSIGNOB TO BELLTELE- PHONE LABORATORIES, INCORPORATED, OF NEW YOBK,.N. Y.,' ACORPORATION OF NEW YORK mncraoorrxoar. svs'rmc Application filed October16, 1928. Serial No. 312,761.

This invention relates to electro-optical systems and more articularlyto a method of and apparatus or producing television images.

An object of the invention is to provide a simple method and means forproducing a photoelectric current having components which correspond,respectively, to simultaneously scanned elemental areas of a field ofview and which can be separated and separately utilized as desired, forexample, for multi-transmission line television.

Another object of the invention isto provide a simple method and meansfor enabling a field of view to be scanned by a plurality of beams oflight simultaneously so as to reduce the time of scanning or to increasethe fineness of grain of the image or to obtain other advantages whichwill be obvious to one skilled in the art.

There is disclosed in a copending application of H. E. Ives, Serial No.291,744, filed July 11, 1928, a scanning disc provided with apertures soarranged that a plurality of elemental areas in different groups arescanned simultaneously,'the light from the elements of one group fallingupon one light sensitive cell and that from the other upon a secondcell. A similar system has been heretofore suggested in which the lightreaching the two cells is constantly interrupted at differentfrequencies, respectively, by means of a scanning disc having twocircular rows of apertures,

, the number of apertures in the two rows being different. The'nesultingphotoelectric variationsare impressed on a single transmission line andlater separated by means of filters. In accordance with the presentinvention, means are provided for producing a photoelectric currenthaving components which correspond, respectively, to simultaneouslyscanned elemental areas of a field of view. In a preferred embodiment ofthe invention a scanning disc is employed for projecting two beams oilight simultaneously upon the field of view so that the field is scannedby two spots of light moving over different courses. Each of these beamsis interrupted or varied inintensity at a distinctive frequency. Lightreflected from the field of view may be reelectromotive force connectedthereto and positioned between two light polarizing prisms. A largenumber of beamsmay, of course, be employed and any suitable means" usedto direct and modulate the beams. The image current produced as theresult of scanning comprises' a plurality of modulated frequencycomponents and these components are preferably separated by means offilters, detected, and transmitted over separate transmission lines,respectively.

Fig. 1. of the accompanying drawings shows, diagrammatically, atelevision system embodying features of the present invention; Fig. 2 isa detail showing of apparatus mlay be employed in the system shown in1g.

Fig. 3 shows a modification of the system shown in Fig. 1; and

Figs. 4: and 5 are detail showings of apparatus employed in the systemshown in Fig. 3.

Referring now to Figs. 1 and 2 of the draw-. ing, the'subject 10 isscanned by light of substantially parallel rays from the light-sources11 and 12 as it passes through apertures 13 of the scanning disc 14which is driven by the" motor 15 at the rate of 16 or more revolutionsper second. The apertures of the scannin disc are arranged in the formof a spiral and are so spaced that alternate linear elements of thefield of view are scanned by light from crystal having a high frequencysource of tures are omitted is employed. The apertures are so arrangedthat the light beam from one source scans one set of linear elementswhile the light beam from the other source scans the interposed linearelements. The rays of light from source 11 after passing through theapertures 13 and the opening in screen 17 passes through a light valvecomprising the crossed Nicol prisms 18 and 19 and the piezoelectriccrystal 20. This light valve arrangement is similar to that disclosed inmy Patent No. 1,632,069, granted June 14, 1927. The intensity of thelight transmitted by this arrangement varies in accordance with thevariations in electromotive force of the source of alternating current21 which has a fre quency f}, this frequency preferably being made equalto the resonant frequency of the crystal so as to cause it to vibrate atits resonant frequency. If desired, a mechanical interrupter may heemployed in place of this light valve. This light of varying intensitytransmitted through the light valve is iflected by the mirror 22. Theglass plate 23 has a very thin coating of silver so that the lightreaching the plate is partly retiected and partly transmitted. Thisplate is so positioned that the light beam reflected by the mirror 22 ispartly transmitted through the plate and the lens 24% and thus reachesthe subject 10. In a similar manner, light from source 12, after passingthrough the apertures in the scanning disc and the opening in screen 30is transmitted through a light valve comprising the crossed Nicol prisms25 and 26 and the piezo-electric crystal 27 which is actuated by theelectromotive force of the source 28 having a frequency The light beamsfrom this source impinge upon the plate 23 and the reflected portion ofthese light beams reaches the subject 10 through the lens 24;. It isthus apparent that the subject is scanned in a plurality of lines two ata time by two separate beams of light which are varied in intensity atdifferent frequencies, respectively. Light reflected from the subject 10reaches the photoelectric cells 31, which are connected in parallel to acommon circuit, and produces therein current having two components ofdifferent high frequency, respectively, (i. e. 2f and 2f:) each of thesecomponents being modulated inaccordance with the tone values ofsuccessive elemental areas of the subject scanned by one of the scanninglight beams. This current is amplified by the amplifier 32 and thenimpressed on the band pass filters 33 and 34. one of which passes onlyone of the modulated components and the other of which passes only theother of the modulated components. These current components are thendetected by the detectors 35 and 36, respectively, amplified by theamplifiers 3-7 and 38, respectively, and transmitted throughtransformers 39 and 40 and over transmission lines ll and 42,respectively, to the receiving station.

Instead of employing the glass plate 23 having a thin coating of silverfor partly transmitting and partly reflecting the light which reachesit, a glass plate shown in Fig. 2 may be employed. This plate hasalternate transparent and light reflecting linear portions 71 and 72,respectively, each linear portion being the width of a scanning line ora scanning light beam. This plate is so positioned that the light beamreflected by the mirror 22 passes through the transparent portions andthe light from source 12 impinges on the reflecting portions] At thereceiving station currents transmitted over lines il and 4-2 areimpressed upon transformers 13 and 44, respectively, and amplified bythe amplifiers 45 and 46, respectively. Two light valves similar tothose employed at the transmitting station one comprising the crossedNicol prisms t7 and 1S and the piezo-electric crystal 49 and the othercomprising the crossed Nicol prisms 50 and 51 and the piezo-electriccrystal are employed for controlling the intensity of light inaccordance with the amplitude variations of the currents transmittedover the lines tl and 42. These currents after being amplified may beimpressed directly on the crystals 49 and 52, respectively, but they arepreferably impressed on the modulators 53 and 54-, respcc tively, whichare supplied from the sources '55 and 56, respectively, withclectromotive forces of a high frequency which are equal to thefrequencies at which the crystals are resonant. Parallel beams of lightfrom source 5'? after being varied in intensity in a cordance with thevariations in image current received over line 41, are transmittedthrough the opening in screen 58 and the apertures in the disc 59 whichis similar to the scanning disc 14; at the transmitting station andwhich is driven in synchroi'iism therewith by the motor 60. Any suitablearrangement may be employed for maintaining the discs 14: and 59 insynchronism and in phase, for example, the system disclosed in PatentNo. 1,763,909, granted to H. M. Stol ler and E. R. Morton, June 17,1930, may be employed. Light from source 57 after being transmittedthrough the apertures of the rotating disc 59 is reflected by the mirror61 and transmitted through the glass plate 62 which is similar to theplate 23 or 70 employed at the transmitting station. In a similar mannerlight from source 63, the intensity of which is controlled in accordancewith the amplitude variations of the image current transmitted over line42, is transmitted through the opening in screen 64 and the apertures ofthe disc 59 and impinges on the plate 62 from which it is reflected.Since the field of view is completely scanned at the transmittingstation 16 or more times per second, which is within the period of thepersistence of vision, an image of the field of view is presented to theobserver 65 by means of two separate moving light beams, one from source57 and one from source 63, these light beams varying in intensity inaccordance with the tone values of successive elemental areas of thesubject 10 scanned by the light beams from sources 11 and 12,respectively, at the transmitting station. It appears to the observerthat the image is formed on the ground glass screen 66 positioned backof the opening in the screen 67.

In the system shown in Figs. 3 to 5 of the drawing, the object 80 isscanned by two moving beams of light simultaneouslyin a manner somewhatsimilar to that described above in connection with Fig. 1. Two sepa ratescanning discs 81 and 82 each having a row of spirally arrangedapertures are employed for scanning separate portions of the object bymeans of light from the sources 83 and 84, respectively. These discs maybe driven by separate motors as shown or by a single motor through amechanical coupling. The light beams from the sources 83 and 84 arevaried in intensity at difi'erent frequencies, respectively, by means ofsuitable light valves or light interrupters 85 and 86, respectively.Each of these light valves may comprise two crossed Nicol prisms 87 and88 and a piezo electric crystal 89 which is energized by theelectromotive force of a source 90 as shown in Fig. 4. Light reflectedfrom the object 80 impinges on the light sensitive surface of thephotoelectric cells 91 and 92 which are connected in parallel to theinput circuit'of the amplifier 93. A battery 130 is provided forenergizing the photoelectric cells. There is thus produced in thecircuit of the photoelectric cells a current having two high frequencycomponents each modulated in accordance with the intensity of the lightfrom the sources 83 and 84 reflected from the object 80. This current isamplified by the amplifier 93 and the two frequency components areseparated by the band pass filters 94 and 95. These current componentsare then detected by the detectors 96 and 97, respectively, amplified bythe amplifiers 98 and 99, respectively, and impressed on transmissionlines 100 and;101 through transformers 102 and 103, respectively.

At the receiving station, two similar sets of apparatus are employed,each for producing one portion of an image of the object 80 which isscanned at the transmitting station by a light beam from one of thelight sources 83 and 84. Each of these sets of apparatus is similar tothat shown and described in detail in Patent No. 1,759,504 granted to F.Gray, May 20,- 1930. Currents transmitted over lines 100 and 101 areimpressed through the three electrode vacuum tubes 106 and 107 and theother of which comprises the vacuum tubes 108 and 109, each set ofvacuum tubes being coupled through a gain control circuit. The outputcurrent of the amplifying circuit comprising the vacuum tubes 106 and107 is impressed on the oscillator-modulator 110 for modulating the highfrequency current produced thereby. The output energy of thisoscillator-modulator is impressed through the variable coupling 111 andthe distributor 112 upon the multiple electrode glow discharge lamp 113.In a similar manner the current transmitted over line 101 and amplifiedby the vacuum tubes 108 and 109 is impressed on the oscillator-modulator114 for modulating the high frequency current produced thereby, and theoutput energy of this oscillator-modulator is impressed through thevariable coupling 115 and the distributor 116 upon the multipleelectrode glow discharge lamp 117. w The discs 81 and 82 at thetransmitting station and the distributors 112 and 116 t the receivingstation are driven in synchronis by their respective driving motors. Asuitable system for controlling the speed of the driving motors tomaintain the driven elements at different stations respectively insynchronism is shown in the patent of H. M. Stoller and E. R. Morton towhich reference is made above. Each of the glow discharge lamps 113 and117 comprises a continuous chamber formed of closely positioned parallelglass tubes 118 (Fig. 5) containing a gas such as neon. The lamp has alarge number of small electrodes 119, one for each elemental area of thefield of view scanned at the transmitting station, which are connectedto the contacts of one of the distributors 112 or 116, and a common gridelectrode 120. Each lamp also has a special set of electrodes 121 whichis continuously energized by the high frequency output energy of one ofthe oscillators 122 or 1 123 for the purpose of preventing lag in theresponse of the lamp to energy supplied to the individual electrodes.The lamp is described in detail in the patent granted to F. Grayreferred to hereinbefore.

It is now known that the width of the frequency band required forproducing electroavoided by actuating a single photoelectric cell, or agroup of cells associated with a single circuit, in accordance with thetone values of several portions of the field of view sin'mltaneously andlater separating the components of the image current each of whichvaries in accordance with the tone values of one of the portions of thefield of view.

What is claimed is:

1. An electro-optical image noducing sys tem comprising means forsuccessively scanning groups of elemental areas of a field of view animage of which is to be produced, each group comprising two separateelemental areas which are scanned simultaneously, and light-sensitivemeans for producing a single photoelectric current having a componentcorresponding to the tone values of each of said simultaneously scannedelemental areas.

2. An electro-optical system comprising means for simultaneouslyproducing a plurality of. separate movable light beams forsimultaneously scanning a plurality of elemental areas of a field ofview, a plurality of elemental areas being scanned in succession by eachbeam, and light-sensitive means for producing a single photoelectriccurrent having a component corresponding to the tone values of each ofat least two of said simultaneously scanned elemental areas.

3. An electroc-optical image producing system comprising means forsimultaneously scanning two elemental areas located in separateportions, respectively, of a field of view an image of which is to beproduced, the elemental areas comprising each of said portions of thefield of view being scanned successively, and light-sensitive means forproducing in a circuit conductively connected to said light-sensitivemeans a single image current having a component corresponding to thetone values of the elemental areas of each of said portions of the fieldof view.

4. An electro-optical system comprising means for simultaneouslyscanning two elemental areas located in separate portions, respectively,of a field of view, the elemental areas comprising each portion of thefield of view being scanned successively, light-sensitive means forproducing in a circuit conductively connected to said light-sensitivemeans a single image current having a component corresponding to thetone values of the elemental areas of each of said portions of the fieldof view, and means for producing a separate current corresponding toeach of said components and having a characteristic thereof.

5. An electro-optical image producing system comprising means forsimultaneously scanning two elemental areas in different groups,respectively, of a field of view an image of which is to be produced,the elemental areas of each group being scanned in succession, and meansincluding a light-sensitive device for producing in a circuitconductively connected to said light-sensitive device, a single imagecurrent comprising components of different frequencies, respectively,each frequency component being modulated in accordance with the tonevalues of the elemental areas of one of said groups, said tone valuesextending over a range of values between fixed limits.

6. An electro-optical system comprising means for simultaneouslyscanning two elemental areas in different groups, respectively, of afield of view, the elemental areas of each group being scanned insuccession, means including a light-sensitive device for producing in acircuit associated therewith an image current comprising components ofdifferent frequencies, respectively, each frequency component beingmodulated in accordance with the tone values of the elemental areas ofone of said groups, a plurality of transmission lines, and means fortransmitting currents corresponding to the amplitude variations of thedifferent modulated frequency components, respectively, over differenttransmission lines.

7. An electro-optical system comprising means for simultaneouslyscanning two elemental areas in different groups, respectively, of afield of view, the elemental areas of each group being scanned insuccession, for producing a single image current having a componentcorresponding to the tone values of the elemental areas of each of saidgroups, respectively, two transmission channels,.and means forseparating said components and impressing them on separate transmissionchannels.

8. An electro-optical system comprising means for simultaneouslyscanning two elemental areas in different groups, respectively, of afield of view, the elemental areas of each group being scanned insuccession, means including a light-sensitive device for producing in acircuit associated therewith an image current comprising components ofdifferent frequencies, respectively, each frequency component beingmodulated in accordance with the tone values of the elemental areas ofone of said groups, means for separating said modulated frequencycomponents, means for demodulating each of said frequency components,two transmission channels, and means for impressing said frequencycomponents after being demodulated on separate transmission channels.

9. An electro-optical system comprising means for simultaneouslyproducing a plurality of separate movable light beams for simultaneouslyscanning different elemental areas of the same field of view, and meansfor modulating said beams at different frequencies, respectively.

10. A method of scanning a field of view which comprises simultaneouslyproducing two separate moving beams of light for scanning differentlines of elemental areas of the field, respectively, and modulating saidbeams at different frequencies, respectively.

11; An electro-optical system comprising means for simultaneouslyproducing a plurality of separate moving beams of light for scanningdifferent lines of elemental areas of a. field of view, respectively,means "for modulating said beams at diiferent frequencies, respectively,and light-sensitive electric means for receiving light reflected fromsaid fieldof view and for setting up an electric current havingcomponents, respectively,

constantly varying at said frequencies, the

amplitude of variation corresponding to the tone values of elementalareas of said field scanned by a beam of corresponding frequency.

12. In combination, a light-sensitive electric element, a source ofdirect current in circuit therewith, a source of light for controlling acharacteristic of said light-sensitive element, means for controllingthe intensity of the light reaching said light-sensitive element forcausing the current in said circuit to vary periodically in accordancewith at least two different frequencies, and a'plurality of electricfilters for selecting current components having said two differentfrequencies, respectively, from said first mentioned current.

13. An electro-optieal image producing system comprising means forsucessively scanning groups of elemental areas of a field of view, eachgroup'comprising two separate elemental areas which are scannedsimultaneously, light-sensitive means for producing a singlephotoelectric current having a component corresponding to the tonevalues of each of said simultaneouslyl scanned elemental areas, meansfor transmitting energy corresponding to the components of saidphotoelectric current and means responsive to said energy for causinglight to be emitted from a plurality of elemental, areas,simultaneously, of an image field corresponding to the scanning of theelemental areas of the field of view, to produce an image of said fieldofview.

14. An electro-optical image producing system comprising means forsimultaneously producing a purality of separate movable light beams forsimultaneously scanning a plurality of elemental areas of a field ofview, a plurality of elemental areas being scanned in succession by eachbeam, light-sensitive means for producing a single photoelectriccurrent-having a component corresponding to the tone values of each ofat least two of said simultaneously scanned elemental areas means forseparately transmitting energy corresponding to each component of saidphotoelectric current and means responsive to said frequencies, theamplitude of variation corresponding to .the tone values of the ele- Imental areas of said field scanned by a beam of corresponding frequency,frequency discriminating means for impressing currents corresponding tosaid components on separate circuits, respectively, means fordemodulating said currents, a plurality of transmission lines forseparately transmitting said demodulated currents, means at the receivinend of said lines for producing a plurality 0 moving beams of light,themovement of said beams corresponding to the movement of said scanningbeams of light, and means controlled by said separately transmittedcurrents for controlling said beams respectively at the receiving end toproduce an image of said field of view. a

16. In an image producing system, means for producing a movable lightbeam for scanning portions of a field of view, means for producing asecond movable light beam for scanning portions of a field of view lyingbetween portions of the field of view scanned by the first mentionedlight beam, and means for causing both said means to operatesimultaneously.

17. In an image producing system, means for producing a movable lightbeam for scanning non-adjacent line series of elemental areas of a fieldof view, means for producing a second movable light beam for scanningline series of elemental areas of said field of view lying betweenthelines scanned by the first mentioned light beam, and means forcausing both said means to operate simultaneously.

18. In an image producing system, a movable light beam for scanningportions of a field of view, means for producing a second movable lightbeam for scanning portions of said field of view lying between portionsof the field of view scanned by the first mentioned light beam, meansfor causing both beam for scanning portions of an object,-

means for producing a second movable light beam for scanning portions ofthe object 1ying between portions scanned by the first mentioned lightbeam, means for causing both said means to operate simultaneously, meansfor giving said light beams a distinctive characteristic, andphotoelectric means having a large photosensitive surface for receivinglight reflected from said object. N V

In witness whereof, I hereunto subscribe my name this 29th day ofSeptember, 1928.

RALPH VJL. HARTLEY.

